In an electrophotographic process or electrostatic recording process, a developer used to visualize an electrostatic image or an electrostatic latent image may include a two-component developer formed of toner and carrier particles and an one-component developer only including toner. The one-component developer may be classified into a magnetic one-component developer and a nonmagnetic one-component developer. A separate fluidizing agent such as colloidal silica is often added to the nonmagnetic one-component developer in order to increase the fluidity of the toner. In general, toner includes coloring particles obtained by dispersing a colorant such as carbon black or other additives in latex and particulating the latex.
Methods of preparing toner include pulverization and polymerization. In pulverization, toner is obtained by melting and mixing synthetic resins, pigments and, if required, other additives, pulverizing the mixture, and sorting the particles until particles having desired size are obtained. In polymerization, a polymerizable monomer composition is manufactured by uniformly dissolving or dispersing various additives such as a pigment, a polymerization initiator and, if required, a cross-linking agent and an antistatic agent in a polymerizable monomer. Then, the polymerizable monomer composition is dispersed in an aqueous dispersive medium containing a dispersion stabilizer by using an agitator so as to form minute liquid droplet particles of the polymerizable monomer composition. Subsequently, the temperature is increased and suspension polymerization is performed to obtain polymerized toner having coloring polymer particles with a desired size.
In an imaging apparatus such as an electrophotographic device or an electrostatic recording device, an electrostatic latent image is formed by exposing the image on a uniformly charged photoreceptor, a toner image is formed by attaching toner to the electrostatic latent image, the toner image is transferred onto a transfer medium such as transfer paper or the like; and a non-fixed toner image is fixed onto the transfer medium by using various methods, including heating, pressurizing, solvent steaming and the like. In most fixing processes, the transfer medium to which the toner image is transferred passes through fixing rollers and pressing rollers and the toner is heated and pressed so as to be fused to the transfer medium.
In images formed by an imaging apparatus such as electrophotocopier, high precision and accuracy need to be improved. In general, toner used in an imaging apparatus is usually obtained by pulverization. In pulverization, color particles having a large range of size distribution may be easily formed. Thus, in order to obtain satisfactory developing properties, there is a need to sort the coloring particles obtained through pulverization according to a size so as to reduce the particle size distribution. However, it is difficult to precisely control the particle size and the particle size distribution by using a general mixing/pulverizing process in the manufacture of toner suitable for an electrophotographic process or an electrostatic recording process. Also, when preparing a fine particle toner, the toner preparation yield is adversely affected by the sorting process. In addition, there are limits in changing/adjusting of a toner design for obtaining desirable charging and fixing properties. Accordingly, polymerized toner in which the size of particles is easily controlled and a complex manufacturing process such as sorting is not needed, have been recently highlighted.
When toner is prepared by the polymerization, polymerized toner having a desired particle size and particle size distribution may be obtained without pulverizing or sorting. However, even if the polymerization is used, agglomeration of latex and a colorant may be inefficient and aluminum-based substances used to form an agglomerating agent may be harmful to both environment and human body.
Also, in order for high gloss of toner and wide fixing regions to be compatible, a capsule-formed toner structure may be used and controlled through an agglomeration process control so as to suppress surface exposure of a colorant and releasing agent and to distribute to charging uniformity, flowability, and thermal storage characteristics. However, if a large amount of releasing amount having a low melting point and low viscosity is contained to improve gloss of a gloss paper, a low molecular part and resin may be compatible to some degree and may be plasticized so that there are problems in thermal storage characteristics and flowability of toner.